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    <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav>  <ul class="sidebar-links"><li><a href="/vdoing-demo-repository/pages/c438df/" class="sidebar-link">01_认识 Python</a></li><li><a href="/vdoing-demo-repository/pages/54ff73/" class="sidebar-link">02_第一个 Python 程序</a></li><li><a href="/vdoing-demo-repository/pages/d84b0c/" class="sidebar-link">03_PyCharm 的初始设置(知道)</a></li><li><a href="/vdoing-demo-repository/pages/d99c19/" class="sidebar-link">04_多文件项目的演练</a></li><li><a href="/vdoing-demo-repository/pages/6bdfff/" 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class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/3ce888/#_02-while-循环基本使用" class="sidebar-link">02. while 循环基本使用</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/3ce888/#_2-1-while-语句基本语法" class="sidebar-link">2.1 while 语句基本语法</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/3ce888/#_2-2-赋值运算符" class="sidebar-link">2.2 赋值运算符</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/3ce888/#_2-3-python-中的计数方法" class="sidebar-link">2.3 Python 中的计数方法</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/3ce888/#_2-4-循环计算" class="sidebar-link">2.4 循环计算</a></li></ul></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/3ce888/#_03-break-和-continue" class="sidebar-link">03. break 和 continue</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/3ce888/#_3-1-break" class="sidebar-link">3.1 break</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/3ce888/#_3-2-continue" class="sidebar-link">3.2 continue</a></li></ul></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/3ce888/#_04-while-循环嵌套" class="sidebar-link">04. while 循环嵌套</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/3ce888/#_4-1-循环嵌套" class="sidebar-link">4.1 循环嵌套</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/3ce888/#_4-2-循环嵌套演练-九九乘法表" class="sidebar-link">4.2 循环嵌套演练 —— 九九乘法表</a></li></ul></li></ul></li><li><a href="/vdoing-demo-repository/pages/ceea69/" class="sidebar-link">13_函数基础</a></li><li><a href="/vdoing-demo-repository/pages/e158a8/" class="sidebar-link">14_高级变量类型</a></li><li><a href="/vdoing-demo-repository/pages/ed6fdd/" class="sidebar-link">15_名片管理系统(综合应用)</a></li><li><a href="/vdoing-demo-repository/pages/e98ba6/" class="sidebar-link">16_变量进阶(理解)</a></li><li><a href="/vdoing-demo-repository/pages/f99095/" class="sidebar-link">17_函数进阶</a></li></ul> </aside> <div><main class="page"><div class="theme-vdoing-wrapper "><div class="articleInfo-wrap" data-v-06225672><div class="articleInfo" data-v-06225672><ul class="breadcrumbs" data-v-06225672><li data-v-06225672><a href="/vdoing-demo-repository/" title="首页" class="iconfont icon-home router-link-active" data-v-06225672></a></li> <li data-v-06225672><a href="/vdoing-demo-repository/python/#Python" data-v-06225672>Python</a></li></ul> <div class="info" data-v-06225672><!----> <div title="创建时间" class="date iconfont icon-riqi" data-v-06225672><a href="javascript:;" data-v-06225672>2023-04-02</a></div> <!----></div></div></div> <!----> <div class="content-wrapper"><div class="right-menu-wrapper"><div class="right-menu-margin"><div class="right-menu-title">目录</div> <div class="right-menu-content"></div></div></div> <h1><img src="">12_循环<!----></h1> <!----> <div class="theme-vdoing-content content__default"><h1 id="循环"><a href="#循环" class="header-anchor">#</a> 循环</h1> <h2 id="目标"><a href="#目标" class="header-anchor">#</a> 目标</h2> <ul><li>程序的三大流程</li> <li>while 循环基本使用</li> <li>break 和 continue</li> <li>while 循环嵌套</li></ul> <h2 id="_01-程序的三大流程"><a href="#_01-程序的三大流程" class="header-anchor">#</a> 01. 程序的三大流程</h2> <ul><li><p>在程序开发中，一共有三种流程方式：</p> <ul><li><strong>顺序</strong> —— <strong>从上向下</strong>，顺序执行代码</li> <li><strong>分支</strong> —— 根据条件判断，决定执行代码的 <strong>分支</strong></li> <li><strong>循环</strong> —— 让 <strong>特定代码 重复</strong> 执行</li></ul> <p><img src="media/14966337488366/001_%E7%A8%8B%E5%BA%8F%E4%B8%89%E5%A4%A7%E6%B5%81%E7%A8%8B.png" alt="001_程序三大流程"></p></li></ul> <h2 id="_02-while-循环基本使用"><a href="#_02-while-循环基本使用" class="header-anchor">#</a> 02. <code>while</code> 循环基本使用</h2> <ul><li><p>循环的作用就是让 <strong>指定的代码</strong> 重复的执行</p></li> <li><p><code>while</code> 循环最常用的应用场景就是 <strong>让执行的代码</strong> 按照 <strong>指定的次数</strong> <strong>重复</strong> 执行</p></li> <li><p>需求 —— 打印 5 遍 <code>Hello Python</code></p></li> <li><p>思考 —— 如果要求打印 100 遍怎么办？</p></li></ul> <h3 id="_2-1-while-语句基本语法"><a href="#_2-1-while-语句基本语法" class="header-anchor">#</a> 2.1 <code>while</code> 语句基本语法</h3> <div class="language-python line-numbers-mode"><pre class="language-python"><code>初始条件设置 —— 通常是重复执行的 计数器

<span class="token keyword">while</span> 条件<span class="token punctuation">(</span>判断 计数器 是否达到 目标次数<span class="token punctuation">)</span><span class="token punctuation">:</span>
    条件满足时，做的事情<span class="token number">1</span>
    条件满足时，做的事情<span class="token number">2</span>
    条件满足时，做的事情<span class="token number">3</span>
    <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">(</span>省略<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
    
    处理条件<span class="token punctuation">(</span>计数器 <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><p><strong>注意</strong>：</p> <ul><li><code>while</code> 语句以及缩进部分是一个 <strong>完整的代码块</strong></li></ul> <h4 id="第一个-while-循环"><a href="#第一个-while-循环" class="header-anchor">#</a> 第一个 while 循环</h4> <p><strong>需求</strong></p> <ul><li>打印 5 遍 Hello Python</li></ul> <div class="language-while line-numbers-mode"><pre class="language-text"><code># 1. 定义重复次数计数器
i = 1

# 2. 使用 while 判断条件
while i &lt;= 5:
    # 要重复执行的代码
    print(&quot;Hello Python&quot;)

    # 处理计数器 i
    i = i + 1

print(&quot;循环结束后的 i = %d&quot; % i)
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br></div></div><blockquote><p>注意：循环结束后，之前定义的计数器条件的数值是依旧存在的</p></blockquote> <h4 id="死循环"><a href="#死循环" class="header-anchor">#</a> 死循环</h4> <blockquote><p>由于程序员的原因，<strong>忘记</strong> 在循环内部 <strong>修改循环的判断条件</strong>，导致循环持续执行，程序无法终止！</p></blockquote> <h3 id="_2-2-赋值运算符"><a href="#_2-2-赋值运算符" class="header-anchor">#</a> 2.2 赋值运算符</h3> <ul><li>在 Python 中，使用 <code>=</code> 可以给变量赋值</li> <li>在算术运算时，为了简化代码的编写，<code>Python</code> 还提供了一系列的 与 <strong>算术运算符</strong> 对应的 <strong>赋值运算符</strong></li> <li>注意：<strong>赋值运算符中间不能使用空格</strong></li></ul> <table><thead><tr><th>运算符</th> <th>描述</th> <th>实例</th></tr></thead> <tbody><tr><td>=</td> <td>简单的赋值运算符</td> <td>c = a + b 将 a + b 的运算结果赋值为 c</td></tr> <tr><td>+=</td> <td>加法赋值运算符</td> <td>c += a 等效于 c = c + a</td></tr> <tr><td>-=</td> <td>减法赋值运算符</td> <td>c -= a 等效于 c = c - a</td></tr> <tr><td>*=</td> <td>乘法赋值运算符</td> <td>c *= a 等效于 c = c * a</td></tr> <tr><td>/=</td> <td>除法赋值运算符</td> <td>c /= a 等效于 c = c / a</td></tr> <tr><td>//=</td> <td>取整除赋值运算符</td> <td>c //= a 等效于 c = c // a</td></tr> <tr><td>%=</td> <td>取 <strong>模</strong> (余数)赋值运算符</td> <td>c %= a 等效于 c = c % a</td></tr> <tr><td>**=</td> <td>幂赋值运算符</td> <td>c **= a 等效于 c = c ** a</td></tr></tbody></table> <h3 id="_2-3-python-中的计数方法"><a href="#_2-3-python-中的计数方法" class="header-anchor">#</a> 2.3 Python 中的计数方法</h3> <p>常见的计数方法有两种，可以分别称为：</p> <ul><li><strong>自然计数法</strong>（从 <code>1</code> 开始）—— 更符合人类的习惯</li> <li><strong>程序计数法</strong>（从 <code>0</code> 开始）—— 几乎所有的程序语言都选择从 0 开始计数</li></ul> <p>因此，大家在编写程序时，应该尽量养成习惯：<strong>除非需求的特殊要求，否则 循环 的计数都从 0 开始</strong></p> <h3 id="_2-4-循环计算"><a href="#_2-4-循环计算" class="header-anchor">#</a> 2.4 循环计算</h3> <blockquote><p>在程序开发中，通常会遇到 <strong>利用循环</strong> <strong>重复计算</strong> 的需求</p></blockquote> <p>遇到这种需求，可以：</p> <ol><li>在 <code>while</code> 上方定义一个变量，用于 <strong>存放最终计算结果</strong></li> <li>在循环体内部，每次循环都用 <strong>最新的计算结果</strong>，<strong>更新</strong> 之前定义的变量</li></ol> <p><strong>需求</strong></p> <ul><li>计算 0 ~ 100 之间所有数字的累计求和结果</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 计算 0 ~ 100 之间所有数字的累计求和结果</span>
<span class="token comment"># 0. 定义最终结果的变量</span>
result <span class="token operator">=</span> <span class="token number">0</span>

<span class="token comment"># 1. 定义一个整数的变量记录循环的次数</span>
i <span class="token operator">=</span> <span class="token number">0</span>

<span class="token comment"># 2. 开始循环</span>
<span class="token keyword">while</span> i <span class="token operator">&lt;=</span> <span class="token number">100</span><span class="token punctuation">:</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span>i<span class="token punctuation">)</span>

    <span class="token comment"># 每一次循环，都让 result 这个变量和 i 这个计数器相加</span>
    result <span class="token operator">+=</span> i

    <span class="token comment"># 处理计数器</span>
    i <span class="token operator">+=</span> <span class="token number">1</span>

<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;0~100之间的数字求和结果 = %d&quot;</span> <span class="token operator">%</span> result<span class="token punctuation">)</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br></div></div><h4 id="需求进阶"><a href="#需求进阶" class="header-anchor">#</a> 需求进阶</h4> <ul><li>计算 0 ~ 100 之间 所有 <strong>偶数</strong> 的累计求和结果</li></ul> <p>开发步骤</p> <ol><li>编写循环 <strong>确认</strong> <strong>要计算的数字</strong></li> <li>添加 <strong>结果</strong> 变量，在循环内部 <strong>处理计算结果</strong></li></ol> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 0. 最终结果</span>
result <span class="token operator">=</span> <span class="token number">0</span>

<span class="token comment"># 1. 计数器</span>
i <span class="token operator">=</span> <span class="token number">0</span>

<span class="token comment"># 2. 开始循环</span>
<span class="token keyword">while</span> i <span class="token operator">&lt;=</span> <span class="token number">100</span><span class="token punctuation">:</span>

    <span class="token comment"># 判断偶数</span>
    <span class="token keyword">if</span> i <span class="token operator">%</span> <span class="token number">2</span> <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">:</span>
        <span class="token keyword">print</span><span class="token punctuation">(</span>i<span class="token punctuation">)</span>
        result <span class="token operator">+=</span> i

    <span class="token comment"># 处理计数器</span>
    i <span class="token operator">+=</span> <span class="token number">1</span>

<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;0~100之间偶数求和结果 = %d&quot;</span> <span class="token operator">%</span> result<span class="token punctuation">)</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br></div></div><h2 id="_03-break-和-continue"><a href="#_03-break-和-continue" class="header-anchor">#</a> 03. break 和 continue</h2> <blockquote><p><code>break</code> 和 <code>continue</code> 是专门在循环中使用的关键字</p></blockquote> <ul><li><code>break</code> <strong>某一条件满足时</strong>，退出循环，不再执行后续重复的代码</li> <li><code>continue</code> <strong>某一条件满足时</strong>，不执行后续重复的代码</li></ul> <blockquote><p><code>break</code> 和 <code>continue</code> 只针对 <strong>当前所在循环</strong> 有效</p></blockquote> <p><img src="media/14966337488366/002_%E5%BE%AA%E7%8E%AF%E6%B5%81%E7%A8%8B%E5%9B%BE.png" alt="002_循环流程图-w400"></p> <h3 id="_3-1-break"><a href="#_3-1-break" class="header-anchor">#</a> 3.1 break</h3> <ul><li><strong>在循环过程中</strong>，如果 <strong>某一个条件满足后</strong>，<strong>不</strong> 再希望 <strong>循环继续执行</strong>，可以使用 <code>break</code> 退出循环</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code>i <span class="token operator">=</span> <span class="token number">0</span>

<span class="token keyword">while</span> i <span class="token operator">&lt;</span> <span class="token number">10</span><span class="token punctuation">:</span>

    <span class="token comment"># break 某一条件满足时，退出循环，不再执行后续重复的代码</span>
    <span class="token comment"># i == 3</span>
    <span class="token keyword">if</span> i <span class="token operator">==</span> <span class="token number">3</span><span class="token punctuation">:</span>
        <span class="token keyword">break</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span>i<span class="token punctuation">)</span>

    i <span class="token operator">+=</span> <span class="token number">1</span>

<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;over&quot;</span><span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br></div></div><blockquote><p><code>break</code> 只针对当前所在循环有效</p></blockquote> <h3 id="_3-2-continue"><a href="#_3-2-continue" class="header-anchor">#</a> 3.2 continue</h3> <ul><li><strong>在循环过程中</strong>，如果 <strong>某一个条件满足后</strong>，<strong>不</strong> 希望 <strong>执行循环代码，但是又不希望退出循环</strong>，可以使用 <code>continue</code></li> <li>也就是：在整个循环中，<strong>只有某些条件</strong>，不需要执行循环代码，而其他条件都需要执行</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code>i <span class="token operator">=</span> <span class="token number">0</span>

<span class="token keyword">while</span> i <span class="token operator">&lt;</span> <span class="token number">10</span><span class="token punctuation">:</span>

    <span class="token comment"># 当 i == 7 时，不希望执行需要重复执行的代码</span>
    <span class="token keyword">if</span> i <span class="token operator">==</span> <span class="token number">7</span><span class="token punctuation">:</span>
        <span class="token comment"># 在使用 continue 之前，同样应该修改计数器</span>
        <span class="token comment"># 否则会出现死循环</span>
        i <span class="token operator">+=</span> <span class="token number">1</span>

        <span class="token keyword">continue</span>

    <span class="token comment"># 重复执行的代码</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span>i<span class="token punctuation">)</span>

    i <span class="token operator">+=</span> <span class="token number">1</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br></div></div><ul><li>需要注意：使用 <code>continue</code> 时，<strong>条件处理部分的代码，需要特别注意</strong>，不小心会出现 <strong>死循环</strong></li></ul> <blockquote><p><code>continue</code> 只针对当前所在循环有效</p></blockquote> <h2 id="_04-while-循环嵌套"><a href="#_04-while-循环嵌套" class="header-anchor">#</a> 04. <code>while</code> 循环嵌套</h2> <h3 id="_4-1-循环嵌套"><a href="#_4-1-循环嵌套" class="header-anchor">#</a> 4.1 循环嵌套</h3> <ul><li><code>while</code> 嵌套就是：<code>while</code> 里面还有 <code>while</code></li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">while</span> 条件 <span class="token number">1</span><span class="token punctuation">:</span>
    条件满足时，做的事情<span class="token number">1</span>
    条件满足时，做的事情<span class="token number">2</span>
    条件满足时，做的事情<span class="token number">3</span>
    <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">(</span>省略<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
    
    <span class="token keyword">while</span> 条件 <span class="token number">2</span><span class="token punctuation">:</span>
        条件满足时，做的事情<span class="token number">1</span>
        条件满足时，做的事情<span class="token number">2</span>
        条件满足时，做的事情<span class="token number">3</span>
        <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">(</span>省略<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
    
        处理条件 <span class="token number">2</span>
    
    处理条件 <span class="token number">1</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br></div></div><h3 id="_4-2-循环嵌套演练-九九乘法表"><a href="#_4-2-循环嵌套演练-九九乘法表" class="header-anchor">#</a> 4.2 循环嵌套演练 —— 九九乘法表</h3> <h4 id="第-1-步-用嵌套打印小星星"><a href="#第-1-步-用嵌套打印小星星" class="header-anchor">#</a> 第 1 步：用嵌套打印小星星</h4> <p><strong>需求</strong></p> <ul><li>在控制台连续输出五行 <code>*</code>，每一行星号的数量依次递增</li></ul> <div class="language- line-numbers-mode"><pre class="language-text"><code>*
**
***
****
*****
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><ul><li>使用字符串 * 打印</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 1. 定义一个计数器变量，从数字1开始，循环会比较方便</span>
row <span class="token operator">=</span> <span class="token number">1</span>

<span class="token keyword">while</span> row <span class="token operator">&lt;=</span> <span class="token number">5</span><span class="token punctuation">:</span>

    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;*&quot;</span> <span class="token operator">*</span> row<span class="token punctuation">)</span>

    row <span class="token operator">+=</span> <span class="token number">1</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><h4 id="第-2-步-使用循环嵌套打印小星星"><a href="#第-2-步-使用循环嵌套打印小星星" class="header-anchor">#</a> 第 2 步：使用循环嵌套打印小星星</h4> <p><strong>知识点</strong> 对 <code>print</code> 函数的使用做一个增强</p> <ul><li><p>在默认情况下，<code>print</code> 函数输出内容之后，会自动在内容末尾增加换行</p></li> <li><p>如果不希望末尾增加换行，可以在 <code>print</code> 函数输出内容的后面增加 <code>, end=&quot;&quot;</code></p></li> <li><p>其中 <code>&quot;&quot;</code> 中间可以指定 <code>print</code> 函数输出内容之后，继续希望显示的内容</p></li> <li><p>语法格式如下：</p></li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 向控制台输出内容结束之后，不会换行</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;*&quot;</span><span class="token punctuation">,</span> end<span class="token operator">=</span><span class="token string">&quot;&quot;</span><span class="token punctuation">)</span>

<span class="token comment"># 单纯的换行</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;&quot;</span><span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><blockquote><p><code>end=&quot;&quot;</code> 表示向控制台输出内容结束之后，不会换行</p></blockquote> <p><strong>假设</strong> <code>Python</code> <strong>没有提供</strong> 字符串的 <code>*</code> 操作 <strong>拼接字符串</strong></p> <p><strong>需求</strong></p> <ul><li>在控制台连续输出五行 <code>*</code>，每一行星号的数量依次递增</li></ul> <div class="language- line-numbers-mode"><pre class="language-text"><code>*
**
***
****
*****
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><p><strong>开发步骤</strong></p> <ul><li>1&gt; 完成 5 行内容的简单输出</li> <li>2&gt; 分析每行内部的 <code>*</code> 应该如何处理？
<ul><li>每行显示的星星和当前所在的行数是一致的</li> <li>嵌套一个小的循环，专门处理每一行中 <code>列</code> 的星星显示</li></ul></li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code>row <span class="token operator">=</span> <span class="token number">1</span>

<span class="token keyword">while</span> row <span class="token operator">&lt;=</span> <span class="token number">5</span><span class="token punctuation">:</span>

    <span class="token comment"># 假设 python 没有提供字符串 * 操作</span>
    <span class="token comment"># 在循环内部，再增加一个循环，实现每一行的 星星 打印</span>
    col <span class="token operator">=</span> <span class="token number">1</span>

    <span class="token keyword">while</span> col <span class="token operator">&lt;=</span> row<span class="token punctuation">:</span>
        <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;*&quot;</span><span class="token punctuation">,</span> end<span class="token operator">=</span><span class="token string">&quot;&quot;</span><span class="token punctuation">)</span>

        col <span class="token operator">+=</span> <span class="token number">1</span>

    <span class="token comment"># 每一行星号输出完成后，再增加一个换行</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;&quot;</span><span class="token punctuation">)</span>

    row <span class="token operator">+=</span> <span class="token number">1</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br></div></div><h4 id="第-3-步-九九乘法表"><a href="#第-3-步-九九乘法表" class="header-anchor">#</a> 第 3 步： 九九乘法表</h4> <p><strong>需求</strong> 输出 九九乘法表，格式如下：</p> <div class="language- line-numbers-mode"><pre class="language-text"><code>1 * 1 = 1	
1 * 2 = 2	2 * 2 = 4	
1 * 3 = 3	2 * 3 = 6	3 * 3 = 9	
1 * 4 = 4	2 * 4 = 8	3 * 4 = 12	4 * 4 = 16	
1 * 5 = 5	2 * 5 = 10	3 * 5 = 15	4 * 5 = 20	5 * 5 = 25	
1 * 6 = 6	2 * 6 = 12	3 * 6 = 18	4 * 6 = 24	5 * 6 = 30	6 * 6 = 36	
1 * 7 = 7	2 * 7 = 14	3 * 7 = 21	4 * 7 = 28	5 * 7 = 35	6 * 7 = 42	7 * 7 = 49	
1 * 8 = 8	2 * 8 = 16	3 * 8 = 24	4 * 8 = 32	5 * 8 = 40	6 * 8 = 48	7 * 8 = 56	8 * 8 = 64	
1 * 9 = 9	2 * 9 = 18	3 * 9 = 27	4 * 9 = 36	5 * 9 = 45	6 * 9 = 54	7 * 9 = 63	8 * 9 = 72	9 * 9 = 81

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><p><strong>开发步骤</strong></p> <ul><li><ol><li>打印 9 行小星星</li></ol></li></ul> <div class="language- line-numbers-mode"><pre class="language-text"><code>*
**
***
****
*****
******
*******
********
*********
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><ul><li><ol start="2"><li>将每一个 <code>*</code> 替换成对应的行与列相乘</li></ol></li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 定义起始行</span>
row <span class="token operator">=</span> <span class="token number">1</span>

<span class="token comment"># 最大打印 9 行</span>
<span class="token keyword">while</span> row <span class="token operator">&lt;=</span> <span class="token number">9</span><span class="token punctuation">:</span>
    <span class="token comment"># 定义起始列</span>
    col <span class="token operator">=</span> <span class="token number">1</span>

    <span class="token comment"># 最大打印 row 列</span>
    <span class="token keyword">while</span> col <span class="token operator">&lt;=</span> row<span class="token punctuation">:</span>

        <span class="token comment"># end = &quot;&quot;，表示输出结束后，不换行</span>
        <span class="token comment"># &quot;\t&quot; 可以在控制台输出一个制表符，协助在输出文本时对齐</span>
        <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;%d * %d = %d&quot;</span> <span class="token operator">%</span> <span class="token punctuation">(</span>col<span class="token punctuation">,</span> row<span class="token punctuation">,</span> row <span class="token operator">*</span> col<span class="token punctuation">)</span><span class="token punctuation">,</span> end<span class="token operator">=</span><span class="token string">&quot;\t&quot;</span><span class="token punctuation">)</span>

        <span class="token comment"># 列数 + 1</span>
        col <span class="token operator">+=</span> <span class="token number">1</span>

    <span class="token comment"># 一行打印完成的换行</span>
    <span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;&quot;</span><span class="token punctuation">)</span>

    <span class="token comment"># 行数 + 1</span>
    row <span class="token operator">+=</span> <span class="token number">1</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br></div></div><p><strong>字符串中的转义字符</strong></p> <ul><li><code>\t</code> 在控制台输出一个 <strong>制表符</strong>，协助在输出文本时 <strong>垂直方向</strong> 保持对齐</li> <li><code>\n</code> 在控制台输出一个 <strong>换行符</strong></li></ul> <blockquote><p><strong>制表符</strong> 的功能是在不使用表格的情况下在 <strong>垂直方向</strong> 按列对齐文本</p></blockquote> <table><thead><tr><th>转义字符</th> <th>描述</th></tr></thead> <tbody><tr><td>\\</td> <td>反斜杠符号</td></tr> <tr><td>\'</td> <td>单引号</td></tr> <tr><td>\&quot;</td> <td>双引号</td></tr> <tr><td>\n</td> <td>换行</td></tr> <tr><td>\t</td> <td>横向制表符</td></tr> <tr><td>\r</td> <td>回车</td></tr></tbody></table></div></div> <!----> <div class="page-edit"><div class="edit-link"><a href="https://github.com/xugaoyi/vuepress-theme-vdoing/edit/master/docs/00.Python/12.循环.md" target="_blank" rel="noopener noreferrer">编辑</a> <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></div> <!----> <!----></div> <div class="page-nav-wapper"><div class="page-nav-centre-wrap"><a href="/vdoing-demo-repository/pages/79d78c/" class="page-nav-centre page-nav-centre-prev"><div class="tooltip">11_运算符</div></a> <a href="/vdoing-demo-repository/pages/ceea69/" class="page-nav-centre page-nav-centre-next"><div class="tooltip">13_函数基础</div></a></div> <div class="page-nav"><p class="inner"><span class="prev">
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